Three UDP-hexose 4-epimerases with overlapping substrate specificity coexist in E. coli O86:B7 |
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Authors: | Guo Hongjie Yi Wen Li Lei Wang Peng George |
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Institution: | Department of Biochemistry, The Ohio State University, Columbus, OH 43210, USA. |
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Abstract: | The O-antigen gene cluster of Escherichia coli O86:B7 was sequenced previously in our lab. One UDP-hexose 4-epimerase gene (named gne2 in this paper) was found and later characterized to be able to catalyze the interconversion between UDP-GlcNAc/GalNAc and UDP-Glc/Gal with almost equal efficiency. However, sequencing of the flanking gene region upstream of the traditional O-antigen gene cluster revealed an open reading frame (gne1), sharing 100% identity with Gne from E. coli O55, previously identified as UDP-GlcNAc 4-epimerase. Furthermore, we also located the traditional galE gene in the gal operon of O86:B7, which can catalyze the interconversion of UDP-Glc to UDP-Gal. Thus, for the first time, three UDP-hexose 4-epimerases with overlapping substrate specificity were found to coexist in one bacterium. Deletion of gne1 and gne2 in O86:B7 produced two different LPS phenotypes: the gne1 mutant exhibited rough LPS, while the gne2 mutant showed semi-rough LPS phenotype. These findings provide new clues for understanding the mechanism of O-antigen biosynthesis. |
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Keywords: | UDP uridine diphosphate GlcNAc N-acetylglucosamine GalNAc N-acetylgalactosamine Gal galactose Glc glucose UndP undecaprenol-phosphate SDR short-chain dehydrogenase/reductase IPTG d-galactospyranoside" target="_blank">isopropyl 1-thio-β-d-galactospyranoside |
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